JP7447909B2 - Polarizing plate, polarizing plate manufacturing method, and liquid crystal display device - Google Patents

Description

The present invention relates to a polarizing plate, a method for manufacturing a polarizing plate, and a liquid crystal display device.

A polarizing plate used in a display device such as a liquid crystal display device includes a polarizer and protective films disposed on both sides of the polarizer. As the protective film, a (meth)acrylic resin film is used because it has excellent transparency, dimensional stability, and low moisture absorption.

Such a polarizing plate includes, for example, a polarizer, a (meth)acrylic resin film (protective film) placed on the viewing side of the polarizer, and a (meth)acrylic resin film (protective film) placed on the liquid crystal cell side of the polarizer. A polarizing plate including a norbornene resin film (protective film) is known (for example, Patent Documents 1 and 2).

By the way, a polarizing plate is usually manufactured through a process of bonding protective films to both sides of a polarizer via an adhesive. The protective film used is formed into a film, wound up into a roll, stored as a roll, and then unwound and used when manufacturing a polarizing plate.

However, while the protective film is stored in a roll for a certain period of time, it tends to undergo winding deformation, which may cause surface defects such as depressions on the surface of the film in the roll. A protective film having such surface defects is not suitable for optical applications.

On the other hand, a method is known in which the surface defects of the protective film before being bonded to the polarizer are repaired by heat-treating the protective film at a predetermined temperature (for example, Patent Documents 1 and 2).

JP2013-254133A Japanese Patent Application Publication No. 2017-120440

However, even if heat treatments such as those shown in Patent Documents 1 and 2 were performed, surface defects such as depressions could not be sufficiently eliminated.

On the other hand, the present inventors have found that by further performing hot water treatment before heat treatment, surface defects associated with winding deformation can be significantly repaired. On the other hand, a new problem was discovered in that hot water treatment tends to cause moisture to remain inside the protective film, which tends to cause ring-shaped unevenness in the resulting liquid crystal display device.

The present invention has been made in view of the above circumstances, and provides a polarizing plate that can suppress ring-shaped unevenness in a liquid crystal display device while repairing surface defects of a protective film, a method for manufacturing the polarizing plate, and a liquid crystal display using the same. The purpose is to provide a display device.

The above problem can be solved by the following configuration.

The polarizing plate of the present invention includes a polarizer, a protective film A disposed on one surface of the polarizer, a protective film B disposed on the other surface of the polarizer, and the polarized light of the protective film B. The protective film B includes a (meth)acrylic resin and rubber particles, and the protective film B includes a (meth)acrylic resin and a rubber particle. is a structural unit derived from methyl methacrylate in an amount of 50 to 95% by mass, and a structural unit derived from phenylmaleimide in an amount of 1 to 25% by mass, based on the total structural units constituting the (meth)acrylic resin. It is a copolymer containing a structural unit derived from 1 to 25% by mass of an acrylic acid alkyl ester, and the equilibrium water content of the protective film A measured at 23°C and 55%RH is a (mass%), When the equilibrium moisture content of the protective film B measured at 23° C. and 55% RH is defined as b (% by mass), the following formula (1) is satisfied.
Formula (1) a<b

The method for producing a polarizing plate of the present invention includes a step of treating the protective film B with hot water of 30°C or higher, and when the glass transition temperature of the protective film B is Tg, the treated protective film B is (Tg -70) to (Tg+10) °C, a step of attaching the heat-treated protective film B to one side of the polarizer, a step of attaching the protective film A to the other side of the polarizer, forming an adhesive layer on the surface of the protective film B opposite to the polarizer, the protective film B containing a (meth)acrylic resin and rubber particles; ) The acrylic resin is derived from 50 to 95% by mass of structural units derived from methyl methacrylate and 1 to 25% by mass of phenylmaleimide, based on the total structural units constituting the (meth)acrylic resin. It is a copolymer containing a structural unit and a structural unit derived from 1 to 25% by mass of an acrylic acid alkyl ester, and the equilibrium moisture content of the protective film A measured at 23°C and 55% RH is a( When b (mass %) is the equilibrium water content of the protective film B measured at 23° C. and 55% RH, the following formula (1) is satisfied.
Formula (1) a<b

The liquid crystal display device of the present invention includes a liquid crystal cell, a first polarizing plate disposed on one surface of the liquid crystal cell, and a second polarizing plate disposed on the other surface of the liquid crystal cell, At least one of the first polarizing plate and the second polarizing plate is the polarizing plate of the present invention, and the adhesive layer of the polarizing plate is bonded to the liquid crystal cell.

According to the present invention, it is possible to provide a polarizing plate that can suppress ring-shaped unevenness in a liquid crystal display device while repairing surface defects of a protective film, a method for manufacturing the polarizing plate, and a liquid crystal display device using the same.

FIG. 1 is a sectional view showing a polarizing plate according to an embodiment of the present invention. FIG. 2 is a sectional view showing a liquid crystal display device according to an embodiment of the present invention.

The present inventors speculate that the causes of ring-shaped unevenness in display devices are mainly due to the following two points.

First, in the manufacturing process of the polarizing plate, when the protective film B is treated with hot water, the water tends to remain unevenly and not completely removed from the inside of the polarizing plate even during the subsequent drying process. Water tends to remain in a ring shape inside the polarizing plate (Factor 1).

Furthermore, if a protective film A with low moisture permeability is placed on the viewing side of the polarizer (the side opposite to the side where the adhesive layer is placed), the moisture remaining in the protective film B will be absorbed by the polarizing plate. It becomes difficult to be discharged to the outside. As a result, moisture tends to accumulate inside the polarizing plate, making ring-shaped unevenness more likely to occur (Factor 2).

In contrast, the present inventors set the equilibrium moisture content b of the protective film B on the liquid crystal cell side of the polarizer (the side on which the adhesive layer is disposed) to be higher than the equilibrium moisture content a of the protective film A on the viewing side. It has been found that by increasing the height, ring-shaped unevenness can be suppressed. This is because the adhesive layer, which easily contains water, is in contact with the protective film B, which makes it easier for moisture in the protective film B (for example, moisture on the polarizer side) to move toward the adhesive layer. This is thought to be because it is easier to be discharged to the outside via the .

In order to make the equilibrium water content b of the protective film B relatively high, it is preferable that the (meth)acrylic resin contained in the protective film B contains a structural unit derived from phenylmaleimide. Since the structural unit derived from phenylmaleimide has a bulky structure, it is easy to form microscopic voids through which water molecules can move in the matrix of the film, and it is easy to move water appropriately. Furthermore, since phenylmaleimide has moderately high polarity, it also has a moderately high affinity with water molecules and easily attracts water molecules.

On the other hand, if the equilibrium water content b of the protective film B is relatively increased too much, the difference in the amount of dimensional change between the protective film B and the protective film A becomes large, which may cause curling of the polarizing plate. In the present invention, since the protective film B contains rubber particles, stress due to dimensional changes due to the inflow and outflow of moisture can be alleviated, so that curling of the polarizing plate can be made less likely to occur.

Embodiments of the present invention will be described in detail below with reference to the drawings.

1. Polarizing Plate FIG. 1 is a sectional view showing a polarizing plate 100 according to the present embodiment.

As shown in FIG. 1, the polarizing plate 100 according to the present embodiment includes a polarizer 110 (polarizer), a protective film 120A (protective film A) disposed on one surface thereof, and a protective film 120A (protective film A) disposed on the other surface. The protective film 120B (protective film B) arranged, the adhesive layer 130A (adhesive layer A) arranged between the protective film 120A and the polarizer 110, and the protective film 120B and the polarizer 110. The adhesive layer 130B (adhesive layer B) is arranged.

Furthermore, the polarizing plate 100 further includes an adhesive layer 140 disposed on the surface of the protective film 120B opposite to the polarizer 110. The adhesive layer 140 is a layer for attaching the polarizing plate 100 to a display element (not shown) such as a liquid crystal cell. The surface of the adhesive layer 140 is usually protected with a release film (not shown).

1-1. Polarizer A polarizer is an element that passes only light with a plane of polarization in a certain direction. The polarizer can typically be a polyvinyl alcohol-based polarizing film. Examples of polyvinyl alcohol polarizing films include polyvinyl alcohol films dyed with iodine and dichroic dyes.

The polyvinyl alcohol polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing it with iodine or a dichroic dye (preferably a film further subjected to durability treatment with a boron compound); It may be a film obtained by dyeing an alcoholic film with iodine or a dichroic dye and then uniaxially stretching the film (preferably, a film further subjected to durability treatment with a boron compound). The absorption axis of polarizer 110 is typically parallel to the direction of maximum stretch.

Examples of polyvinyl alcohol-based polarizing films include those described in JP-A-2003-248123, JP-A-2003-342322, etc. with an ethylene unit content of 1 to 4 mol%, a degree of polymerization of 2000 to 4000, and a degree of saponification of 99. 0 to 99.99 mol% of ethylene-modified polyvinyl alcohol is used.

The thickness of the polarizer is preferably 5 to 30 μm, and more preferably 5 to 20 μm from the viewpoint of making the polarizing plate thinner.

1-2. Protective film A
The protective film A is not particularly limited as long as it is a transparent resin film. From the viewpoint of improving wet heat durability, the equilibrium moisture content a (mass %) of the protective film A is preferably lower than the equilibrium moisture content b (mass %) of the protective film B. That is, it is preferable that the protective film A satisfies the relationship of the following formula (1).
Formula (1) a<b

The equilibrium moisture content a of the protective film A is preferably less than 1.5% by mass. When the equilibrium water content a of the protective film A is low, it is difficult for moisture in the environment to penetrate into the inside of the polarizing plate, so it is easy to suppress deterioration of the polarizer due to the moisture. The equilibrium moisture content a of the protective film A is more preferably 0.3 to 1.4% by mass.

The equilibrium moisture content a of the protective film A can be measured by the following procedure.
1) After controlling the humidity at 23° C. and 55% RH for 48 hours, the weight of the protective film is measured (weight M1). Weight measurement is performed at 23° C. and 55% RH.
2) Next, the protective film is dried in an oven at 130°C for 8 hours. Thereafter, the weight (weight M2) of the protective film is measured in the same manner as described above.
3) Calculate the equilibrium water content by applying the weights M1 and M2 obtained in 1) and 2) above to the following formula.
Equilibrium water content (mass%) = {(M1-M2)/M2}×100

The equilibrium water content a of the protective film A can be adjusted by the composition of the film (particularly the types of resin and additives). In order to lower the equilibrium water content a of the protective film A, the resin contained in the protective film A must be a resin with lower polarity than the resin contained in the protective film B (containing a structural unit derived from a monomer having a polar group). It is preferable to use a small amount of resin).

The resin constituting the protective film A is not particularly limited as long as it satisfies the equilibrium water content relationship described above, but for example, the resin may have a low content of structural units derived from a monomer having a polar group such as phenylmaleimide. Alternatively, it may be a (meth)acrylic resin, a polyester resin, or a cycloolefin resin that does not contain it.

1-2-1. Resin ((meth)acrylic resin)
The (meth)acrylic resin contained in the protective film A may be a homopolymer containing a structural unit derived from methyl methacrylate, or may be a homopolymer containing a structural unit derived from methyl methacrylate and methacrylic resin copolymerizable with it. A copolymer containing a structural unit derived from a copolymerizable monomer other than methyl acid may also be used.

The copolymerizable monomer is not particularly limited, and the alkyl group other than methyl methacrylate has 1 to 1 carbon atoms, such as ethyl (meth)acrylate, propyl (meth)acrylate, and six-membered ring lactone (meth)acrylate. 18 (meth)acrylic acid esters; α, β-unsaturated acids such as (meth)acrylic acid; unsaturated group-containing dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; styrene, α-methylstyrene α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; maleimides such as maleimide and N-substituted maleimide; maleic anhydride and glutaric anhydride. One type of copolymerizable monomer may be used, or two or more types may be used in combination.

Among them, the (meth)acrylic resin contained in the protective film A includes α,β-unsaturated acids, unsaturated group-containing dicarboxylic acids, α,β-unsaturated nitriles, maleimides, maleic anhydride, It is preferable that the content of structural units derived from a copolymerized monomer having a polar group such as glutaric anhydride is lower than that of the (meth)acrylic resin of the protective film B, or is not contained. Among these, a homopolymer of methyl methacrylate (polymethyl methacrylate) is preferred from the viewpoint of easily adjusting the equilibrium water content of the protective film A within the above range.

The content of structural units derived from methyl methacrylate is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, based on the total structural units constituting the (meth)acrylic resin. . The type and composition of the monomer of the (meth)acrylic resin can be identified by ¹ H-NMR.

The glass transition temperature (Tg) of the (meth)acrylic resin is preferably 90°C or higher, more preferably 100 to 150°C. The protective film A in which the (meth)acrylic resin has a Tg of 90° C. or higher can have good heat resistance.

The glass transition temperature (Tg) of a (meth)acrylic resin can be measured using DSC (Differential Scanning Colorimetry) in accordance with JIS K 7121-2012 or ASTM D 3418-82. .

The weight average molecular weight (Mw) of the (meth)acrylic resin is not particularly limited and can be appropriately set depending on the film forming method. For example, when the protective film A is formed by melt casting, the weight average molecular weight of the (meth)acrylic resin is preferably 100,000 to 300,000. When the protective film A is formed by a solution casting method, the weight average molecular weight of the (meth)acrylic resin is preferably from 400,000 to 3,000,000, more preferably from 500,000 to 2,000,000. When the weight average molecular weight of the (meth)acrylic resin is within the above range, sufficient mechanical strength (toughness) can be imparted to the film without impairing film formability.

The weight average molecular weight (Mw) of the (meth)acrylic resin can be measured in terms of polystyrene by gel permeation chromatography (GPC). Specifically, it can be measured using a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL in series, manufactured by Tosoh Corporation). The measurement conditions may be the same as in the examples described later.

The content of the (meth)acrylic resin is preferably 60% by mass or more, more preferably 70% by mass or more, based on the protective film A.

(polyester resin)
Examples of polyester resins include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Among them, polyethylene terephthalate (PET) is preferred.

(Cycloolefin resin)
The cycloolefin resin is not particularly limited, but is preferably a polymer containing a structural unit derived from a norbornene monomer having a polar group, from the viewpoint of ease of film formation by a solution casting method.

The norbor monomer having a polar group is represented by the following formula (2).

At least one of R ¹ to R ⁴ in formula (2) is preferably a polar group. Examples of polar groups include carboxy groups, hydroxy groups, alkoxycarbonyl groups, aryloxycarbonyl groups, amino groups, amide groups, cyano groups, and groups in which these groups are bonded via linking groups such as alkylene groups. included. Cycloolefin resins that have structural units derived from norbornene monomers that have polar groups are not only easy to dissolve in solvents when forming films using the solution casting method, but also have low glass transition properties in the resulting films. Can increase temperature. Among these, the polar group is preferably an alkoxycarbonyl group, more preferably an alkoxycarbonyl group having 1 to 10 carbon atoms.

The remainder of R ¹ to R ⁴ are each preferably a hydrogen atom or a hydrocarbon group. The hydrocarbon group may be a hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms. Examples of hydrocarbon groups include alkyl groups and aryl groups. The hydrocarbon group may further have a substituent.

For example, R ¹ in formula (2) may be a polar group, and R ² , R ³ and R ⁴ may each be a hydrogen atom or a hydrocarbon group; R ¹ and R ³ may each be a polar group. , and R ² and R ⁴ may each be a hydrogen atom or a hydrocarbon group.

p and m are each integers from 0 to 3. Among these, m+p is preferably 0 to 4, more preferably 0 to 2, and even more preferably m=1 and p=0.

The content of the structural unit derived from the norbornene monomer having a polar group is preferably 20 to 100% by mass, and 30 to 100% by mass based on the total structural units constituting the cycloolefin resin. It is more preferable.

The cycloolefin resin may further contain a structural unit derived from another monomer copolymerizable with the norbornene monomer having a polar group. Examples of other monomers that can be copolymerized include cycloolefin monomers that do not have a norbornene skeleton, such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene. Among these, the number of carbon atoms in the cycloolefin monomer is preferably 4 to 20, more preferably 5 to 12.

Among these, it is preferable that the protective film A contains a (meth)acrylic resin.

1-2-2. Other Components The protective film A may further contain other components other than those mentioned above, if necessary. Examples of other ingredients include rubber particles, matting agents, ultraviolet absorbers, and the like.

In particular, when the protective film A contains a (meth)acrylic resin, it may further contain rubber particles from the viewpoint of eliminating the brittleness of the film.

Examples of the rubber particles contained in the protective film A include those similar to the rubber particles contained in the protective film B, which will be described later. The content of rubber particles in the protective film A can be adjusted depending on the purpose. For example, from the viewpoint of making it easier to satisfy the above equilibrium water content relationship, the content of rubber particles in the protective film A is preferably greater than the content of rubber particles in the protective film B. On the other hand, from the viewpoint of easily suppressing the curling of the polarizing plate due to the difference in the amount of dimensional change, the content of rubber particles in the protective film A is about the same as the content of rubber particles described later in the protective film B (for example, It is preferable that the absolute value of the difference in the content of rubber particles between film A and protective film B is 5% by mass or less.

A matting agent may be added from the viewpoint of imparting slipperiness to the film. Examples of matting agents include inorganic fine particles such as silica particles, organic fine particles having a glass transition temperature of 80° C. or higher, and the like.

Examples of UV absorbers include benzotriazole UV absorbers, benzophenone UV absorbers, salicylic acid ester UV absorbers, cyanoacrylate UV absorbers, and triazine UV absorbers. Among these, benzotriazole-based UV absorbers and benzophenone-based UV absorbers are preferred, and benzotriazole-based UV absorbers are more preferred in terms of having good UV absorption ability.

(thickness)
The thickness of the protective film A is not particularly limited, but from the viewpoint of easily suppressing curling of the polarizing plate, the thickness of the protective film A may be greater than or approximately the same as the thickness of the protective film B. Specifically, the thickness of the protective film A is preferably 10 to 100 μm, more preferably 20 to 80 μm.

1-3. Protective film B
When used as a display device, the protective film B is disposed between a polarizer and a display element such as a liquid crystal cell, and can function as a retardation film for adjusting retardation. As mentioned above, the protective film B in the polarizing plate has been treated with hot water. Protective film B contains (meth)acrylic resin and rubber particles.

1-3-1. The equilibrium water content b (mass%) of the (meth)acrylic resin protective film B is determined from the equilibrium water content a ( It is preferable that it is higher than (mass%). That is, it is preferable that the equilibrium moisture content b of the protective film B at 23° C. and 55% RH satisfies the relationship of the above-mentioned formula (1).

The equilibrium water content b of the protective film B is preferably 1.5 to 2.2% by mass. When the equilibrium moisture content b of the protective film B is 1.5% by mass or more, it is easy for moisture to pass through appropriately, so moisture can be easily discharged toward the adhesive layer, and moisture is unlikely to remain inside the polarizing plate. When the equilibrium moisture content b of the protective film B is 2.2% by mass or less, the difference in the amount of dimensional change due to the difference in equilibrium moisture content between the protective film B and the protective film A is not too large, so that curling of the polarizing plate is prevented. Easy to suppress. From the same viewpoint, the equilibrium water content b of the protective film B is more preferably 1.5 to 2.0% by mass.

The difference in equilibrium moisture content (ba) between the protective film B and the protective film A is preferably 0.1 to 2.0% by mass. When the difference in equilibrium moisture content is 0.1% by mass or more, moisture that has entered during the manufacturing process of the polarizing plate is easily moved toward the adhesive layer. Thereby, ring-shaped unevenness of the polarizing plate can be easily suppressed. On the other hand, if the difference in equilibrium moisture content is 2.0% by mass or less, the difference in dimensional change due to the difference in equilibrium moisture content between protective film B and protective film A is not too large, so for example, polarized light during drying, etc. The board is less likely to curl. The difference in equilibrium water content (ba) between the protective film B and the protective film A is more preferably 0.5 to 1.5% by mass, especially from the viewpoint of further suppressing ring-shaped unevenness of the polarizing plate. .

The relationship between the equilibrium moisture contents of the protective film B and the protective film A can be adjusted by the equilibrium moisture contents of the protective film B and the protective film A. As mentioned above, the equilibrium water content of the protective film B depends on the monomer composition of the (meth)acrylic resin (specifically, the content of the structural unit (U2) derived from phenylmaleimide) and the content of rubber particles. It can be adjusted by In order to increase the equilibrium water content b of the protective film B, it is preferable to use, for example, a (meth)acrylic resin containing a structural unit (U2) derived from phenylmaleimide as a monomer having a polar group.

The (meth)acrylic resin contained in the protective film B is a structural unit derived from methyl methacrylate (U1) from the viewpoint of adjusting the equilibrium water content of the protective film B within the above range and improving brittleness. , a structural unit (U2) derived from phenylmaleimide, and a structural unit (U3) derived from an acrylic acid alkyl ester.

The content of the structural unit (U1) derived from methyl methacrylate is preferably 50 to 95% by mass, and preferably 70 to 90% by mass, based on the total structural units constituting the (meth)acrylic resin. is more preferable.

Since the structural unit (U2) derived from phenylmaleimide has appropriate polarity, it can increase the affinity with moisture. Further, since the structural unit (U2) derived from phenylmaleimide has a relatively bulky structure, it may have micro voids that can move water into the resin matrix. Thereby, the moisture mobility and drainage of the protective film B can be improved.

The content of the structural unit (U2) derived from phenylmaleimide is preferably 1 to 25% by mass based on the total structural units constituting the (meth)acrylic resin. When the content of the structural unit (U2) derived from phenylmaleimide is 1% by mass or more, it has appropriate polarity, so it not only has an affinity with water molecules but also creates micro-pores through which water molecules can move. Because it has a sufficient amount, it is easy to increase the equilibrium moisture content. When the content of the structural unit (U2) derived from phenimaleimide is 25% by mass or less, the brittleness of the protective film B is less likely to be impaired. From the above viewpoint, the content of the structural unit (U2) derived from phenylmaleimide is more preferably 7 to 15% by mass.

The structural unit (U3) derived from an acrylic acid alkyl ester has a good affinity with rubber particles containing a structural unit derived from butyl acrylate, for example, because the polymer (b) constituting the shell portion has a good affinity with rubber particles. Can improve dispersibility.

The acrylic acid alkyl ester is preferably an acrylic acid alkyl ester in which the alkyl moiety has 1 to 7 carbon atoms, preferably 1 to 5 carbon atoms. Examples of acrylic acid alkyl esters include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, and the like.

The content of the structural unit (U3) derived from acrylic acid alkyl ester is preferably 1 to 25% by mass based on the total structural units constituting the (meth)acrylic resin. When the content of the structural unit (U3) derived from acrylic acid alkyl ester is 1% by mass or more, appropriate flexibility can be imparted to the (meth)acrylic resin, so the film does not become too brittle and is difficult to break. . When the content of the structural unit (U3) derived from acrylic acid alkyl ester is 25% by mass or less, the Tg of the (meth)acrylic resin does not decrease too much, so the heat resistance of the protective film B is not easily impaired. There is no damage to the mechanical strength. From the above viewpoint, the content of structural units derived from acrylic acid alkyl ester is more preferably 5 to 15% by mass.

The ratio of the structural unit (U2) derived from phenylmaleimide to the total amount of the structural unit (U2) derived from phenylmaleimide and the structural unit (U3) derived from acrylic acid alkyl ester shall be 20 to 70% by mass. is preferred. When the ratio is 20% by mass or more, the heat resistance of the protective film B is easily increased, and when the ratio is 70% by mass or less, the protective film B does not become too brittle.

The glass transition temperature (Tg) of the (meth)acrylic resin is preferably 110°C or higher, more preferably 120 to 150°C. When the Tg of the (meth)acrylic resin is within the above range, the heat resistance of the protective film B can be easily improved. In order to adjust the Tg of the (meth)acrylic resin, it is preferable to adjust the content of the structural unit (U2) derived from phenylmaleimide or the structural unit (U3) derived from acrylic acid alkyl ester, for example.

The weight average molecular weight (Mw) of the (meth)acrylic resin is preferably 500,000 or more. When the weight average molecular weight of the (meth)acrylic resin is 500,000 or more, the viscosity of the dope used for solution casting does not become too low, which not only suppresses aggregation of rubber particles but also makes the surface of the protective film B flat. It is also possible to suppress a decrease in sexual performance. Furthermore, when the weight average molecular weight of the (meth)acrylic resin is 500,000 or more, sufficient mechanical strength (toughness) can be imparted to the protective film B. From the above viewpoint, the weight average molecular weight of the (meth)acrylic resin is more preferably from 500,000 to 3,000,000, and even more preferably from 600,000 to 2,000,000. The weight average molecular weight can be measured by the same method as described above.

The content of the (meth)acrylic resin is preferably 60% by mass or more, more preferably 70% by mass or more, based on the protective film B.

1-3-2. Rubber particles (rubber particles)
The rubber particles may have a function of imparting toughness (flexibility) to the protective film B. Rubber particles are particles that include a rubbery polymer. The rubbery polymer is a flexible crosslinked polymer with a glass transition temperature of 20° C. or lower. Examples of such crosslinked polymers include butadiene-based crosslinked polymers, (meth)acrylic-based crosslinked polymers, and organosiloxane-based crosslinked polymers. Among these, (meth)acrylic crosslinked polymers are preferred from the viewpoint of having a small refractive index difference with (meth)acrylic resins and the transparency of the protective film B is less likely to be impaired, and acrylic crosslinked polymers (acrylic rubber-like polymer) is more preferred.

That is, the rubber particles are preferably particles containing the acrylic rubbery polymer (a).

Regarding the acrylic rubbery polymer (a):
The acrylic rubbery polymer (a) is a crosslinked polymer containing a structural unit derived from an acrylic ester as a main component. Containing as a main component means that the content of structural units derived from acrylic ester is within the range described below. The acrylic rubbery polymer (a) contains a structural unit derived from an acrylic ester, a structural unit derived from another monomer copolymerizable with it, and two or more radically polymerizable groups ( A crosslinked polymer containing a structural unit derived from a polyfunctional monomer having a non-conjugated reactive double bond is preferable.

Acrylic acid esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, and acrylic acid. Preferably, it is an acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms, such as n-octyl acid. The number of acrylic esters may be one type or two or more types.

The content of structural units derived from acrylic ester is preferably 40 to 80% by mass, and preferably 50 to 80% by mass, based on the total structural units constituting the acrylic rubbery polymer (a1). is more preferable. When the content of acrylic ester is within the above range, sufficient toughness can be easily imparted to the protective film.

The other copolymerizable monomers are monomers copolymerizable with the acrylic ester other than polyfunctional monomers. That is, the copolymerizable monomer does not have two or more radically polymerizable groups. Examples of copolymerizable monomers include methacrylic acid esters such as methyl methacrylate; styrenes such as styrene and methylstyrene; (meth)acrylonitrile; (meth)acrylamides; (meth)acrylic acid . Among these, the other copolymerizable monomers preferably include styrenes. The number of other copolymerizable monomers may be one, or two or more.

The content of structural units derived from other copolymerizable monomers is preferably 5 to 55% by mass, and 10 to 55% by mass, based on the total structural units constituting the acrylic rubbery polymer (a). More preferably, it is 45% by mass.

Examples of polyfunctional monomers include allyl (meth)acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl maleate, divinyl adipate, divinylbenzene, ethylene glycol di(meth)acrylate, diethylene glycol ( Contains meth)acrylate, triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethanetetra(meth)acrylate, dipropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate .

The content of the structural unit derived from the polyfunctional monomer is preferably 0.05 to 10% by mass, and 0.1% by mass based on the total structural units constituting the acrylic rubbery polymer (a). More preferably, it is 5% by mass. If the content of the polyfunctional monomer is 0.05% by mass or more, the degree of crosslinking of the obtained acrylic rubber-like polymer (a) is likely to be increased, so that the hardness and rigidity of the obtained film are impaired too much. First, when the content is 10% by mass or less, the toughness of the film is less likely to be impaired.

The monomer composition constituting the acrylic rubbery polymer (a) can be measured, for example, by the peak area ratio detected by pyrolysis GC-MS.

The glass transition temperature (Tg) of the rubbery polymer is preferably 0°C or lower, more preferably -10°C or lower. When the glass transition temperature (Tg) of the rubbery polymer is 0° C. or lower, appropriate toughness can be imparted to the film. The glass transition temperature (Tg) of the rubbery polymer is measured in the same manner as described above.

The glass transition temperature (Tg) of the rubbery polymer can be adjusted by the composition of the rubbery polymer. For example, in order to lower the glass transition temperature (Tg) of the acrylic rubbery polymer (a), an acrylic ester with an alkyl group having 4 or more carbon atoms/ It is preferable to increase the mass ratio of other copolymerizable monomers (eg, 3 or more, preferably 4 to 10).

Particles containing an acrylic rubbery polymer (a) are particles made of an acrylic rubbery polymer (a), or a hard layer made of a hard crosslinked polymer (c) having a glass transition temperature of 20° C. or higher. , and a soft layer made of the acrylic rubbery polymer (a) arranged around the particles (these are also referred to as "elastomers"); or the acrylic rubbery polymer (a) The particles may be made of an acrylic graft copolymer obtained by polymerizing a mixture of monomers such as methacrylic acid ester in at least one stage in the presence of. The particles made of the acrylic graft copolymer may be core-shell particles having a core portion containing the acrylic rubbery polymer (a) and a shell portion covering the core portion.

Regarding core-shell type rubber particles containing acrylic rubbery polymer:
(core part)
The core portion contains an acrylic rubber-like polymer (a), and may further contain a hard crosslinked polymer (c) if necessary. That is, the core portion may have a soft layer made of an acrylic rubber-like polymer and a hard layer made of a hard crosslinked polymer (c) disposed inside the soft layer.

The crosslinked polymer (c) may be a crosslinked polymer containing methacrylic acid ester as a main component. That is, the crosslinked polymer (c) has a structural unit derived from a methacrylic acid alkyl ester, a structural unit derived from another monomer copolymerizable with it, and a structural unit derived from a polyfunctional monomer. It is preferable that it is a crosslinked polymer containing.

The methacrylic acid alkyl ester may be the above-mentioned methacrylic acid alkyl ester; other copolymerizable monomers may be the above-mentioned styrenes, acrylic esters, etc.; the polyfunctional monomer is The same monomers as those listed above as the polyfunctional monomers may be mentioned.

The content of the structural unit derived from the methacrylic acid alkyl ester may be 40 to 100% by mass based on the total structural units constituting the crosslinked polymer (c). The content of structural units derived from other copolymerizable monomers may be 60 to 0% by mass based on the total structural units constituting the other crosslinked polymer (c). The content of the structural unit derived from the polyfunctional monomer may be 0.01 to 10% by mass based on the total structural units constituting the other crosslinked polymer.

(shell part)
The shell portion includes a methacrylic polymer (b) (another polymer) containing as a main component a structural unit derived from a methacrylic acid ester, which is graft-bonded to the acrylic rubbery polymer (a). Containing as a main component means that the content of the structural unit derived from methacrylic acid ester is within the range described below.

The methacrylic acid ester constituting the methacrylic polymer (b) is preferably an alkyl methacrylic ester having an alkyl group of 1 to 12 carbon atoms, such as methyl methacrylate. The number of methacrylic esters may be one, or two or more.

The content of methacrylic acid ester is preferably 50% by mass or more based on the total structural units constituting the methacrylic polymer (b). When the content of methacrylic acid ester is 50% by mass or more, compatibility with a methacrylic resin containing a structural unit derived from methyl methacrylate as a main component is easily obtained. From the above viewpoint, the content of the methacrylic acid ester is more preferably 70% by mass or more based on the total structural units constituting the methacrylic polymer (b).

The methacrylic polymer (b) may further contain a structural unit derived from another monomer copolymerizable with the methacrylic acid ester. Examples of other copolymerizable monomers include acrylic esters such as methyl acrylate, ethyl acrylate, and n-butyl acrylate; benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, Includes (meth)acrylic monomers (ring-containing (meth)acrylic monomers) having an alicyclic ring, a heterocyclic ring, or an aromatic ring, such as phenoxyethyl (meth)acrylate.

The content of structural units derived from copolymerizable monomers is preferably 50% by mass or less, and 30% by mass or less based on the total structural units constituting the methacrylic polymer (b). is more preferable.

The ratio of the graft component (grafting ratio) in the rubber particles is preferably 10 to 250% by mass, more preferably 15 to 150% by mass. When the grafting rate is above a certain level, the ratio of the graft component, that is, the methacrylic polymer (b) whose main component is a structural unit derived from methacrylic acid ester, is appropriately high, so that the bond between the rubber particles and the methacrylic resin is Easily increases compatibility and makes rubber particles more difficult to aggregate. In addition, the rigidity of the film is less likely to be impaired. When the graft ratio is below a certain level, the proportion of the acrylic rubber-like polymer (a) does not become too small, so that the effect of improving the toughness and brittleness of the film is less likely to be impaired.

Grafting rate is measured by the following method.
1) Dissolve 2 g of core-shell type particles in 50 ml of methyl ethyl ketone and centrifuge for 1 hour at 30,000 rpm and 12°C using a centrifuge (manufactured by Hitachi Koki Co., Ltd., CP60E) to separate insoluble and possible components. Separate into soluble components (centrifugation is performed 3 times in total).
2) The weight of the obtained insoluble matter is applied to the following formula to calculate the grafting rate.
Grafting rate (mass%) = [{(mass of methyl ethyl ketone insoluble matter) - (mass of acrylic rubbery polymer (a))}/(mass of acrylic rubbery polymer (a))] x 100

The average aspect ratio and average major axis of the rubber particles can be calculated by the following method.
1) Observe the cross section of the protective film B using a TEM. The observation area may be an area corresponding to the thickness of the protective film B, or may be an area of 5 μm x 5 μm. When the observation area is an area corresponding to the thickness of the protective film B, the number of measurement points can be one. When the observation area is a 5 μm×5 μm area, the number of measurement points can be four.
2) Measure the major axis and minor axis of each rubber particle in the obtained TEM image, and calculate the aspect ratio. The average value of the aspect ratios obtained from a plurality of rubber particles is defined as an "average aspect ratio", and the average value of the major diameters obtained from a plurality of rubber particles is defined as an "average major axis".

The content of rubber particles is not particularly limited, but is preferably 5 to 25% by mass, more preferably 5 to 15% by mass, based on the protective film B.

The content of rubber particles in the protective film B can be adjusted depending on the purpose. For example, the content of rubber particles in the protective film B is preferably lower than the content of rubber particles in the protective film A from the viewpoint of making it easier to satisfy the above relationship of equilibrium water content. From the viewpoint of easily suppressing the curling of the polarizing plate due to the difference in the amount of dimensional change, the content of rubber particles in the protective film B is about the same as the content of rubber particles in the protective film A (for example, the content of rubber particles in the protective film A and the protective film It is preferable that the difference in the content of rubber particles in film B is 5% by mass or less.

1-3-3. Other Components The protective film B may further contain other components other than those mentioned above, if necessary. For other components, the same components as those in the protective film A can be used.

1-3-4. Physical properties (internal haze)
The internal haze of the protective film B is preferably 1.0% or less, more preferably 0.1% or less, and even more preferably 0.05% or less. The internal haze of the protective film B can be measured by the same method as described above. The internal haze of the protective film B can be adjusted by adjusting the content of rubber particles.

(Phase difference Ro and Rt)
For example, from the viewpoint of using the protective film B as a retardation film for IPS mode, the in-plane retardation Ro measured at a measurement wavelength of 550 nm and in an environment of 23° C. and 55% RH is 0 to 10 nm. It is preferably 0 to 5 nm, more preferably 0 to 5 nm. The retardation Rt of the protective film B in the thickness direction is preferably -20 to 20 nm, more preferably -10 to 10 nm.

Ro and Rt are each defined by the following formula.
Formula (2a): Ro=(nx-ny)×d
Formula (2b): Rt=((nx+ny)/2-nz)×d
(In the formula,
nx represents the refractive index in the in-plane slow axis direction (direction where the refractive index is maximum) of the film,
ny represents the refractive index in the direction perpendicular to the in-plane slow axis of the film,
nz represents the refractive index in the thickness direction of the film,
d represents the thickness (nm) of the film. )

The in-plane slow axis of the protective film B can be confirmed using an automatic birefringence meter Axo Scan Mueller Matrix Polarimeter (manufactured by Axometrics).

Ro and Rt can be measured by the following method.
1) Humidify the protective film in an environment of 23° C. and 55% RH for 24 hours. The average refractive index of this film is measured using an Abbe refractometer, and the thickness d is measured using a commercially available micrometer.
2) The retardation Ro and Rt of the film after humidity conditioning at a measurement wavelength of 550 nm were measured at 23° C. and 55% RH using an automatic birefringence meter Axo Scan Mueller Matrix Polarimeter (manufactured by Axometrix). Measure under environmental conditions.

The retardation Ro and Rt of the protective film B can be adjusted by, for example, the monomer composition of the (meth)acrylic resin and the stretching conditions.

(Residual solvent amount)
Since the protective film B is preferably formed by a casting method, it may further contain a residual solvent. The amount of residual solvent is preferably 700 ppm or less, more preferably 30 to 700 ppm, based on the protective film B. The content of the residual solvent can be adjusted by the drying conditions of the dope cast on the support in the process of manufacturing the protective film.

The amount of residual solvent in the protective film B can be measured by headspace gas chromatography. In the headspace gas chromatography method, a sample is sealed in a container, heated, and while the container is filled with volatile components, the gas in the container is immediately injected into a gas chromatograph and mass spectrometry is performed to identify the compound. The volatile components are quantified while the test is being carried out. In the headspace method, it is possible to observe all peaks of volatile components using a gas chromatograph, and by using an analysis method that utilizes electromagnetic interaction, it is also possible to quantify volatile substances and monomers with high precision. It can be done at the same time.

(thickness)
The thickness of the protective film B is not particularly limited, but from the viewpoint of easily suppressing curling of the polarizing plate, it should be thinner than or approximately the same as the thickness of the protective film A (the difference in thickness between the protective films B and A). may be, for example, 50 μm or less). Specifically, the thickness of the protective film B is preferably, for example, 5 to 60 μm, more preferably 10 to 50 μm.

1-3-5. Method for manufacturing protective films A and B Protective films A and B may be manufactured by any method, and may be manufactured by a melt casting method or a solution casting method.

Among these, it is preferable that at least the protective film B be manufactured by a solution casting method from the viewpoint of being able to use a high molecular weight (meth)acrylic resin. That is, the protective film B includes at least 1) a step of obtaining a dope containing the above-mentioned (meth)acrylic resin, rubber particles, and a solvent, and 2) a step of casting the obtained dope onto a support. , drying and peeling to obtain a film-like product, and 3) drying the obtained film-like product while stretching as necessary, and preferably further 4) the obtained protection. It can be manufactured through a process of winding up a film to obtain a roll body.

Regarding the step 1), a dope is prepared by dissolving or dispersing a (meth)acrylic resin and rubber particles in a solvent.

The solvent used for the dope contains at least an organic solvent (good solvent) that can dissolve the (meth)acrylic resin. Examples of good solvents include chlorinated organic solvents such as methylene chloride; non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran. Among these, methylene chloride is preferred.

The solvent used for the dope may further contain a poor solvent. Examples of poor solvents include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. When the ratio of alcohol in the dope becomes high, the film-like material tends to gel and easily peel off from the metal support. Examples of straight-chain or branched aliphatic alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Among these, ethanol is preferred because of its dope stability, relatively low boiling point, and good drying properties.

Regarding the step 2), the obtained dope is cast onto a support. The dope can be cast by being discharged from a casting die.

Next, the solvent in the dope cast onto the support is evaporated and dried. The dried dope is peeled off from the support to obtain a film-like product.

The amount of residual solvent in the dope when it is peeled off from the support (the amount of residual solvent in the film-like material when it is peeled off) is preferably, for example, 25% by mass or more, and more preferably 30 to 37% by mass. When the amount of residual solvent at the time of peeling is 37% by mass or less, it is easy to prevent the film-like material from stretching too much due to peeling.

The amount of residual solvent in the dope at the time of peeling is defined by the following formula. The same applies to the following.
Amount of residual solvent in dope (mass%) = (mass of dope before heat treatment - mass of dope after heat treatment) / mass of dope after heat treatment x 100
Note that the heat treatment when measuring the amount of residual solvent refers to heat treatment at 140° C. for 30 minutes.

The amount of residual solvent at the time of peeling can be adjusted by adjusting the drying temperature and drying time of the dope on the support, the temperature of the support, and the like.

Regarding step 3): Dry the obtained film-like material. Drying may be performed in one step or in multiple steps. Moreover, drying may be performed while stretching as necessary.

For example, the process of drying a film-like material includes a step of pre-drying the film-like material (pre-drying step), a step of stretching the film-like material (stretching step), and a step of drying the film-like material after stretching (main drying step). drying step).

(Pre-drying process)
The pre-drying temperature (drying temperature before stretching) can be higher than the stretching temperature. Specifically, it is preferably (Tg-50) to (Tg+50)°C, where Tg is the glass transition temperature of the (meth)acrylic resin. If the pre-drying temperature is (Tg - 50) °C or higher, the solvent will easily evaporate to an appropriate degree, making it easier to improve transportability (handling properties), and if it is below (Tg + 50) °C, the solvent will not volatilize too much. , the stretchability in the subsequent stretching step is less likely to be impaired. In the case of (a) drying using a non-contact heating type while conveying with a tenter stretching machine or rollers, the initial drying temperature can be measured as the temperature inside the stretching machine or the ambient temperature such as the hot air temperature.

(Stretching process)
Stretching may be carried out according to the required optical properties, and it is preferable to stretch in at least one direction, and in two directions perpendicular to each other (for example, in the width direction (TD direction) of the film-like material and in the direction perpendicular thereto). Biaxial stretching in the transport direction (MD direction) may also be performed.

The stretching ratio when producing the protective film B is preferably 5 to 100%, more preferably 20 to 100%. In the case of biaxial stretching, the stretching ratio in each direction is preferably within the above range.

The stretching ratio (%) is defined as (stretching direction size of the film after stretching−stretching direction size of the film before stretching)/(stretching direction size of the film before stretching)×100. In addition, when performing biaxial stretching, it is preferable to set it as the said stretching magnification about each of TD direction and MD direction.

As described above, the stretching temperature (drying temperature during stretching) is preferably Tg (°C) or higher, where Tg is the glass transition temperature of the (meth)acrylic resin, and (Tg + 10) to (Tg + 50). It is more preferable that the temperature is ℃. When the stretching temperature is Tg (°C) or higher, preferably (Tg + 10)°C or higher, the solvent is easily volatilized to an appropriate extent, making it easy to adjust the stretching tension to an appropriate range; does not volatilize too much, so stretchability is less likely to be impaired. The stretching temperature during production of the protective film B can be, for example, 115° C. or higher. As for the stretching temperature, it is preferable to measure the ambient temperature such as (a) the temperature inside the stretching machine, as described above.

The amount of residual solvent in the film-like material at the start of stretching is preferably about the same as the amount of residual solvent in the film-like material at the time of peeling, for example, preferably 20 to 30% by mass, and 25 to 30% by mass. % is more preferable.

Stretching of the film-like material in the TD direction (width direction) can be carried out, for example, by fixing both ends of the film-like material with clips or pins and widening the interval between the clips or pins in the traveling direction (tenter method). Stretching of the film-like material in the MD direction can be carried out, for example, by a method (roll method) in which a plurality of rolls are provided with a difference in peripheral speed and the difference in peripheral speed between the rolls is utilized.

(Main drying process)
From the viewpoint of further reducing the amount of residual solvent, it is preferable to further dry the film-like material obtained after stretching. For example, it is preferable to further dry the film-like material obtained after stretching while conveying it with a roll or the like.

The main drying temperature (drying temperature in the case of unstretched) is preferably (Tg-50) to (Tg-30)°C, where Tg is the glass transition temperature of the (meth)acrylic resin; -40) to (Tg-30)°C is more preferable. If the post-drying temperature is (Tg-50)°C or higher, the solvent can be sufficiently volatilized and removed from the stretched film, and if it is below (Tg-30)°C, the deformation of the film can be seriously prevented. can be suppressed. As for the main drying temperature, it is preferable to measure the atmospheric temperature such as (a) hot air temperature, as described above.

Regarding step 4) It is preferable that the obtained protective film has a long shape. The elongated protective film is wound into a roll to form a roll body.

The length of the long protective film is not particularly limited, but may be, for example, about 100 to 10,000 m. Further, the width of the protective film is preferably 1 m or more, more preferably 1.3 to 4 m.

1-4. Adhesive layer A and B
Adhesive layer A is placed between the protective film A and the polarizer and bonds them together. Similarly, the adhesive layer B is placed between the protective film B and the polarizer to bond them together.

Adhesive layers A and B may be layers obtained from a completely saponified polyvinyl alcohol aqueous solution (water paste), or may be layers of a cured product of an active energy ray-curable adhesive. From the viewpoint of having high affinity with the protective films A and B and facilitating good adhesion, the adhesive layers A and B are preferably cured layers of an active energy ray-curable adhesive.

The active energy ray-curable adhesive may be a photo-radical polymerizable composition or a photo-cationic polymerizable composition. Among these, photocationic polymerizable compositions are preferred.

The cationic photopolymerizable composition includes an epoxy compound and a cationic photopolymerization initiator.

An epoxy compound is a compound having one or more, preferably two or more, epoxy groups in the molecule. Examples of epoxy compounds include hydrogenated epoxy compounds obtained by reacting alicyclic polyols with epichlorohydrin (glycidyl ether of polyols having an alicyclic ring); aliphatic polyhydric alcohols or their alkylenes; Aliphatic epoxy compounds such as oxide adduct polyglycidyl ether; alicyclic epoxy compounds having one or more epoxy groups bonded to an alicyclic ring in the molecule are included. The epoxy compounds may be used alone or in combination of two or more.

The photocationic polymerization initiator may be, for example, an aromatic diazonium salt; an onium salt such as an aromatic iodonium salt or an aromatic sulfonium salt; or an iron-arene complex.

The cationic photopolymerization initiator may be a cationic polymerization accelerator such as oxetane or polyol, a photosensitizer, an ion trapping agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, or a fluid. It may further contain additives such as regulators, plasticizers, antifoaming agents, antistatic agents, leveling agents, and solvents.

The thickness of the adhesive layers A and B is not particularly limited, but may be, for example, about 0.01 to 10 μm, preferably about 0.01 to 5 μm.

1-5. Adhesive Layer The adhesive layer is arranged on the surface of the protective film B opposite to the polarizer. The adhesive layer is a layer for bonding the polarizing plate of the present invention to a display element such as a liquid crystal cell.

The adhesive layer is preferably formed by drying and partially crosslinking an adhesive composition containing a base polymer, a prepolymer and/or a crosslinking monomer, a crosslinking agent, and a solvent. That is, at least a portion of the adhesive composition may be crosslinked.

Examples of adhesive compositions include acrylic adhesive compositions using (meth)acrylic polymers as a base polymer, silicone adhesive compositions using silicone polymers as a base polymer, and rubber-based adhesive compositions using rubber as a base polymer. Includes adhesive compositions. Among these, acrylic pressure-sensitive adhesive compositions are preferred from the viewpoints of transparency, weather resistance, heat resistance, and processability.

The (meth)acrylic polymer contained in the acrylic pressure-sensitive adhesive composition may be a copolymer of a (meth)acrylic acid alkyl ester, a crosslinking agent, and a crosslinkable functional group-containing monomer.

The (meth)acrylic acid alkyl ester is preferably an acrylic acid alkyl ester in which the alkyl group has 2 to 14 carbon atoms.

Examples of functional group-containing monomers that can be crosslinked with a crosslinking agent include amide group-containing monomers, carboxyl group-containing monomers (such as acrylic acid), and hydroxyl group-containing monomers (such as hydroxyethyl acrylate).

Examples of the crosslinking agent contained in the acrylic pressure-sensitive adhesive composition include epoxy crosslinking agents, isocyanate crosslinking agents, peroxide crosslinking agents, and the like. The content of the crosslinking agent in the adhesive composition may be, for example, 0.01 to 10 parts by weight, based on 100 parts by weight of the base polymer (solid content).

The adhesive composition may contain tackifiers, plasticizers, glass fibers, glass beads, metal powder, other fillers, pigments, colorants, fillers, antioxidants, ultraviolet absorbers, and silane coupling, as required. The composition may further contain various additives such as additives.

The equilibrium moisture content of the adhesive layer is usually higher than the equilibrium moisture content b of the protective film B. Thereby, the moisture contained in the protective film B can be discharged from the adhesive layer.

The thickness of the adhesive layer is usually about 3 to 100 μm, preferably 5 to 50 μm.

The surface of the adhesive layer is protected by a release film that has been subjected to release treatment. Examples of release films include plastic films such as acrylic films, polycarbonate films, polyester films, and fluororesin films.

2. Method for manufacturing a polarizing plate The polarizing plate of the present invention is produced by the steps of (1) treating the protective film B with hot water, (2) heat treating the protective film B treated with warm water, and (3) protecting the heat-treated protective film B. A step of laminating film B on one side of the polarizer and laminating protective film A on the other side of the polarizer, and (4) applying an adhesive layer on the side of protective film B opposite to the polarizer. It is manufactured through the process of forming.

Note that polarizing plates are usually manufactured using a roll-to-roll process. Therefore, the protective film A, the protective film B, and the polarizer are each unwound from a roll body and used. Each step will be explained below.

Regarding the step (1) (hot water treatment step), the protective film B is treated with hot water. This allows the protective film B to absorb moisture and loosen easily, thereby making it easier to repair surface defects caused by heat treatment.

The temperature of the hot water is preferably 30°C or higher. If the temperature of the hot water is 30°C or higher, not only will moisture be easily absorbed by the protective film B, but even if deformations or defects occur due to tight winding, the deformations or defects can be repaired by subsequent heat treatment. . Therefore, defects in the polarizing plate caused by the protective film B can be suppressed. From the same viewpoint, the temperature of the hot water is more preferably 40 to 80°C.

The treatment time may be as long as it can eliminate the deformation and defects of the protective film B, and although it depends on the temperature of the hot water, it is preferably 10 to 70 seconds, and preferably 20 to 60 seconds. More preferred.

The treatment method is not particularly limited, and the protective film B may be immersed in warm water, or the protective film B may be sprayed with hot water. The protective film B can be immersed in hot water by, for example, running a long protective film in a bathtub filled with hot water.

Regarding the step (2) (heat treatment step) Next, the protective film B that has been treated with hot water is heat treated. By performing the heat treatment, the moisture taken into the protective film B by the hot water treatment is removed, and deformations and defects caused by tight winding are repaired.

The temperature of the heat treatment is preferably (Tg-70) to (Tg+10)° C., where Tg is the glass transition temperature of the protective film B. If the temperature is (Tg-70)°C or higher, even if the protective film B has deformation or defects due to tight winding, they can be sufficiently repaired. Further, residual moisture in the protective film B, which causes ring-shaped unevenness in the polarizing plate, can also be reduced. When the heat treatment temperature is below (Tg+10° C.), the protective film B is less likely to be thermally deformed or stretched, so that not only the optical properties are less likely to be impaired, but also the polarizing plate is less likely to curl. For the same reason, the temperature of the heat treatment is preferably (Tg-50) to (Tg-10)°C.

Although the heat treatment time depends on the heat treatment temperature, it is preferably 10 to 60 seconds, for example. When the heat treatment time is 10 seconds or more, deformations and defects caused by tight winding of the protective film can be sufficiently repaired. When the heat treatment time is 60 seconds or less, stretching of the protective film due to heat can be suppressed. From the same viewpoint, the heat treatment time is more preferably 15 to 30 seconds.

The heat treatment method is not particularly limited, but can be performed by passing a protective film through a heating furnace.

Regarding the step (3) (bonding step), heat-treated protective film B is bonded to one surface of the polarizer, and protective film A is bonded to the other surface of the polarizer. The bonding can be performed using an adhesive.

The protective films A and B before lamination may be subjected to pretreatment such as corona treatment, if necessary.

For example, when using an active energy ray-curable adhesive as the adhesive, 3a) the surface of the heat-treated protective film B is subjected to surface treatment such as corona treatment, if necessary. Next, a heat-treated protective film B is laminated on one side of the polarizer via a layer of active energy ray curable adhesive, and then active energy rays are irradiated to form the active energy ray curable adhesive. Let it harden. Thereby, the polarizer and the heat-treated protective film B are bonded together via the cured layer of the active energy ray-curable adhesive.

Similarly, 3b) the surface of the protective film A is subjected to surface treatment such as corona treatment, if necessary. Next, the protective film A is laminated on the other surface of the polarizer via a layer of active energy ray curable adhesive, and then active energy rays are irradiated to cure the active energy ray curable adhesive. Thereby, the polarizer and the protective film A are bonded together via the cured layer of the active energy ray-curable adhesive.

Steps 3a) and 3b) may be performed simultaneously or sequentially. From the viewpoint of increasing production efficiency, it is preferable to perform steps 3a) and 3b) simultaneously.

When performing steps 3a) and 3b) at the same time, the lamination of the protective film (for example, protective film B), the polarizer, and the other protective film (for example, protective film A) is preferably performed by a roll-to-roll method. Then, the obtained laminate may be irradiated with active energy rays to cure the active energy ray-curable adhesive.

Regarding the step (4) (adhesive layer forming step) Next, an adhesive layer and its release film are further attached to the surface of the obtained protective film B opposite to the polarizer. Specifically, the adhesive layer can be formed on the protective film B by a method such as transferring a release film provided with an adhesive layer.

In the present invention, the equilibrium moisture contents of the protective films A and B satisfy the above-mentioned relationship of formula (1). As a result, even if the polarizing plate is manufactured without sufficiently removing the water contained in the step (1) above (hot water treatment step) from the protective film B, the water will be transferred from the protective film B to the adhesive layer. and can be discharged. Thereby, ring-shaped unevenness caused by moisture being trapped inside the polarizing plate can be suppressed.

In addition, from the viewpoint of highly suppressing defects in the polarizing plate due to surface defects of the protective film, it is preferable to further perform the steps (1) and (2) above for the protective film A as well.

3. Liquid Crystal Display Device The liquid crystal display device of the present invention includes a liquid crystal cell, a first polarizing plate placed on one side of the liquid crystal cell, and a second polarizing plate placed on the other side of the liquid crystal cell. At least one of the first polarizing plate and the second polarizing plate is the polarizing plate of the present invention.

FIG. 2 is a sectional view showing a liquid crystal display device according to an embodiment of the present invention. As shown in FIG. 2, the liquid crystal display device 200 of the present invention includes a liquid crystal cell 210, a first polarizing plate 220 and a second polarizing plate 230 that sandwich the liquid crystal cell 210, and a backlight 240.

The display mode of the liquid crystal cell 210 is, for example, STN (Super-Twisted Nematic), TN (Twisted Nematic), OCB (Optically Compensated Bend), HAN (Hybridaligned Nematic), VA (Vertical Alignment), MVA (Multi-domain Vertical Alignment), This may be PVA (Patterned Vertical Alignment), IPS (In-Plane-Switching), or the like. For example, in a liquid crystal display device for portable equipment, the IPS mode is preferable.

The first polarizing plate 220 is placed on the viewing side surface of the liquid crystal cell 210 with an adhesive layer 224 in between. The first polarizing plate 220 includes a first polarizer 221, a protective film 222 (F1) placed on the viewing side surface of the first polarizer 221, and a protective film 222 (F1) placed on the liquid crystal cell side surface of the first polarizer 221. a protective film 223 (F2), and two adhesive layers 225 disposed between the first polarizer 221 and the protective film 222 (F1) and between the first polarizer 221 and the protective film 223 (F2). including.

The second polarizing plate 230 is placed on the backlight 240 side surface of the liquid crystal cell 210 with an adhesive layer 234 in between. The second polarizing plate 230 includes a second polarizer 231, a protective film 232 (F3) disposed on the surface of the second polarizer 231 on the liquid crystal cell 210 side, and a surface of the second polarizer 231 on the backlight 240 side. The protective film 233 (F4) placed in agent layer 235.

It is preferable that the absorption axis of the first polarizer 221 and the absorption axis of the second polarizer 231 are perpendicular to each other (cross Nicols). Note that the unit composed of the liquid crystal cell 210, the first polarizing plate 220, and the second polarizing plate 230 is also referred to as a liquid crystal display panel 250.

At least one of the first polarizing plate 220 and the second polarizing plate 230 is the polarizing plate of the present invention. That is, when the first polarizing plate 220 is the polarizing plate of the present invention, the protective film 222 (F1) is the protective film A (protective film 120A in FIG. 1), and the protective film 223 (F2) is the protective film B. (protective film 120B in FIG. 1), and the adhesive layer 224 is an adhesive layer (adhesive layer 140A in FIG. 1). Similarly, when the second polarizing plate 230 is the polarizing plate of the present invention, the protective film 233 (F4) is the protective film A (protective film 120A in FIG. 1), and the protective film 232 (F3) is the protective film B (protective film 120B in FIG. 1), and the adhesive layer 234 is an adhesive layer (adhesive layer 140A in FIG. 1).

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

1. Materials for the protective film (1) Resin The following resins 1 to 5 were prepared.
Resin 1: MMA/PMI/BA copolymer (80/10/10 mass ratio), Tg: 120°C, Mw: 2 million Resin 2: MMA/PMI/MA copolymer (80/10/10 mass ratio) , Tg: 119°C, Mw: 2 million Resin 3: PMMA, Tg: 106°C, Mw: 1 million Resin 4: Polyethylene terephthalate (PET), Tg: 151°C
Resin 5: triacetyl cellulose (TAC), Tg: 160°C
Resin 6: Methyl methacrylate/methyl acrylate copolymer (96/4 mass ratio)
Resin 7: Norbornene resin

The glass transition temperature and weight average molecular weight of Resins 1 to 5 were measured by the following methods.

(Glass-transition temperature)
The glass transition temperature (Tg) of the resin was measured using DSC (Differential Scanning Colorimetry) in accordance with JIS K 7121-2012.

(Weight average molecular weight)
The weight average molecular weight (Mw) of the resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) and a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL series manufactured by Tosoh Corporation). 20 mg±0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this solution was injected into a column (temperature: 40°C), measured with a detector RI temperature of 40°C, and the value converted to styrene was used.

(2) Rubber particles Acrylic rubber particles M-210 (core part: multilayered acrylic rubber-like polymer, shell part: methacrylic acid ester polymer containing methyl methacrylate as the main component) core-shell type rubber Tg of particles, acrylic rubber-like polymer: approximately -10°C, average particle diameter: 220 nm)

The average particle diameter of the rubber particles was measured by the following method.
(Average particle size)
The dispersed particle size of the rubber particles in the obtained dispersion was measured using a zeta potential/particle size measuring system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

2. Production or preparation of protective film <Production of protective film 101>
(Preparation of rubber particle dispersion)
10 parts by mass of rubber particles and 190 parts by mass of methylene chloride were stirred and mixed with a dissolver for 50 minutes, and then dispersed using a Milder dispersion machine (manufactured by Pacific Kiko Co., Ltd.) at 1500 rpm to disperse the rubber particles. I got the liquid.

(Preparation of dope)
Next, a dope having the following composition was prepared. First, methylene chloride and ethanol were added to a pressurized dissolution tank. Next, Resin 1 was charged into a pressurized dissolution tank while being stirred. Next, the rubber particle dispersion prepared above was added and completely dissolved while stirring. This was filtered using SHP150 manufactured by Loki Techno Co., Ltd. to obtain a dope.
Resin 1 ((meth)acrylic resin): 100 parts by mass Methylene chloride: 200 parts by mass Ethanol: 40 parts by mass Rubber particle dispersion: 200 parts by mass

(Film forming)
Next, film formation was performed using the dope after storage. Specifically, the dope was uniformly cast onto a stainless steel belt support with a width of 1800 mm at a temperature of 30° C. using an endless belt casting apparatus. The temperature of the stainless steel belt was controlled at 28°C.

The solvent was evaporated on a stainless steel belt support until the amount of residual solvent in the cast dope became 30% by mass. Then, it was peeled off from the stainless steel belt support at a peeling tension of 128 N/m to obtain a film-like material. The amount of residual solvent in the film-like material at the time of peeling was 30% by mass.

Next, the obtained film-like material was stretched by 20% in the width direction (TD direction) using a tenter at 140° C. (Tg+20° C.) while conveying the peeled film with a large number of rollers. After that, it was further dried at 100°C (Tg - 20°C) while being transported by rolls, and the ends sandwiched with tenter clips were slit and wound up into a roll with a length of 3000 m, a width of 1.5 m, and a film thickness of 40 μm. A protective film 101 (roll body) was obtained.

<Production of protective films 102 to 105 and 108 to 110>
Protective films 102 to 105 and 108 to 110 were obtained in the same manner as protective film 101 except that the type of resin and the content of rubber particles were changed as shown in Table 1.

<Protective film 106>
A polyethylene terephthalate film (Cosmoshine A4100 manufactured by Toyobo Co., Ltd.) was prepared as the protective film 106.

<Protective film 107>
A triacetyl cellulose film (KC4UAW manufactured by Konica Minolta) was prepared as the protective film 107.

<Evaluation>
The equilibrium moisture content of the obtained protective films 101 to 110 was measured by the following method.

(Equilibrium moisture content)
After the obtained protective film was conditioned for 48 hours at 23° C. and 55% RH, the weight of the protective film was measured under the same conditions (weight M1). Thereafter, the protective film was dried in an oven at 130° C. for 8 hours, and then its weight (weight M2) was measured in the same manner. Then, the obtained weights M1 and M2 were applied to the following formula to calculate the equilibrium water content.
Equilibrium water content (mass%) = {(M1-M2)/M2}×100

Table 1 shows the evaluation results for the protective films 101 to 110.

3. Material of polarizing plate <Preparation of polarizer>
A polyvinyl alcohol film with a thickness of 25 μm was swollen with water at 35°C. The obtained film was immersed for 60 seconds in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water, and further immersed in an aqueous solution at 45°C consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched at a stretching temperature of 55°C and a stretching ratio of 5 times. This uniaxially stretched film was washed with water and then dried to obtain a polarizer with a thickness of 12 μm.

<Preparation of ultraviolet curable adhesive composition>
After mixing the following components, defoaming was performed to prepare an ultraviolet curable adhesive composition.
3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate: 45 parts by mass Epolead GT-301 (alicyclic epoxy resin manufactured by Daicel): 40 parts by mass 1,4-butanediol diglycidyl ether: 15 Parts by mass Triarylsulfonium hexafluorophosphate: 2.3 parts by mass (solid content)
9,10-dibutoxyanthracene: 0.1 part by mass 1,4-diethoxynaphthalene: 2.0 parts by mass The triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution.

<Preparation of adhesive composition>
(Preparation of adhesive composition)
An isocyanate crosslinking agent (trade name: Takenate D110N, trimethylolpropane xylylene diisocyanate) is added to 100 parts by mass of the solid content of a (meth)acrylic polymer solution that does not have structural units derived from acid components (carboxyl group-containing monomers). , manufactured by Mitsui Chemicals, Inc., and 0.4 parts by mass of benzoyl peroxide, a peroxide crosslinking agent (trade name: Nyper BMT, manufactured by Nippon Oil & Fats Co., Ltd.), and stirred. Thus, an adhesive composition (acrylic adhesive composition) was obtained.

(Preparation of adhesive layer)
The obtained adhesive composition was uniformly coated with a fountain coater on a 38 μm thick polyethylene terephthalate film (PET film, release film) treated with a silicone release agent, and then heated at 155°C with air circulation. It was dried in a constant temperature oven for 2 minutes to form an adhesive layer with a thickness of 20 μm. Thereby, a PET film with an adhesive layer was obtained.

4. Preparation and evaluation of polarizing plate <Preparation of polarizing plate 201>
(1) Hot water treatment of protective films A and B After producing the protective film A as described above, the protective film 105 is unwound from a roll that has been stored for a certain period of time, and heated with 50°C hot water while applying a tension of 300N in the transport direction. The sample was passed through a tank filled with water for 60 seconds to perform hot water treatment.
Similarly, as the protective film B, after the above fabrication, the protective film 101 is unwound from the roll body stored for a certain period of time, and placed in a tank filled with 50° C. hot water for 60 seconds while applying a tension of 300 N in the transport direction. The mixture was passed through the water and subjected to hot water treatment.

(2) Heat treatment of protective films A and B Next, the hot water-treated protective film 105 (protective film A) was placed in a heating furnace maintained at 76°C (Tg-30°C) while applying a tension of 300N in the transport direction. was passed for 30 seconds to perform heat treatment.
Similarly, the hot water-treated protective film 101 (protective film B) is passed through a heating furnace maintained at 90° C. (Tg-30° C.) for 30 seconds while applying a tension of 300 N in the transport direction. Heat treatment was performed.

(3) Bonding Next, the bonded surfaces of the heat-treated protective films 105 and 101 were each subjected to a corona discharge treatment at a corona output strength of 2.0 kW and a line speed of 18 m/min.

Next, the ultraviolet curable adhesive composition prepared above is applied to the corona discharge treated surfaces of the protective films 105 and 101 using a bar coater so that the film thickness after curing is approximately 3 μm, thereby forming an ultraviolet curable adhesive. A coating layer was formed.

Then, a protective film 105 (protective film A) is applied to one surface of the above-produced polarizer via an ultraviolet curable adhesive layer, and a protective film 101 (protective film A) is attached to the other surface via an ultraviolet curable adhesive layer. The protective films B) were laminated together to obtain a laminate. The bonding was performed so that the absorption axis of the polarizer and the slow axis of the protective film were perpendicular to each other.

Next, the obtained laminate was irradiated with ultraviolet rays using an ultraviolet irradiation device with a belt conveyor (the lamp used was a D bulb manufactured by Fusion UV Systems) so that the cumulative light amount was 750 mJ/cm ² , The UV curable adhesive layer was cured.

Then, on the protective film 101 of the obtained laminate, the above-produced PET film with an adhesive layer is laminated to form a protective film 105 (protective film A)/adhesive layer/polarizer/adhesive layer/protective film. A polarizing plate 201 having a laminated structure of 101 (protective film B)/adhesive layer/PET film was obtained.

<Production of polarizing plates 202 to 207, 215 and 216>
Polarizing plates 202 to 207, 215 and 216 were obtained in the same manner as polarizing plate 201 except that the combination of protective films A and B was changed as shown in Table 2.

<Production of polarizing plates 208 to 214>
Polarizing plates 208 to 214 were obtained in the same manner as polarizing plate 201, except that the hot water treatment and heat treatment conditions of protective films A and B were changed as shown in Table 2.

<Production of polarizing plate 217>
Polarizing plate 217 was obtained in the same manner as polarizing plate 201 except that protective film A was not subjected to hot water treatment or heat treatment.

<Production of polarizing plate 218>
Polarizing plate 218 was obtained in the same manner as polarizing plate 206 with respect to protective films A and B, except that hot water treatment was not performed and only heat treatment was performed.

<Evaluation>
Surface defects and curls of the obtained polarizing plate and ring-shaped unevenness of the liquid crystal display device were measured by the following method.

(Surface defects)
The obtained polarizing plate was cut into 100 sheets using a cutter to the size of a 55-inch display (about 122 cm x about 69 cm). Of the 100 cut polarizing plates, the number of polarizing plates with uneven defects caused by the protective film was counted. Then, surface defects were evaluated based on the following criteria.
◎: 5 or less polarizing plates with uneven defects ○: 6 to 10 polarizing plates with uneven defects △○: 11 to 15 polarizing plates with uneven defects △: 16 or more polarizing plates with uneven defects 20 sheets ×: 21 or more polarizing plates with uneven defects If the number is △ or more, it was judged as good.

(Polarizing plate curl)
The obtained polarizing plate was cut into a size of 30 cm x 30 cm. The obtained polarizing plate sample was placed so that the convex surface of the sample faced the stage surface. Then, the height of each of the four corners a to d of the polarizing plate sample from the stage surface was measured and applied to the following relational expression to determine the amount of curl C.
C=[(Ha+Hb+Hc+Hd)/4]/L
Ha: Height of corner a from the stage surface (mm)
Hb: Height of corner b from the stage surface (mm)
Hc: Height of corner c from the stage surface (mm)
Hd: Height of corner d from stage surface (mm)
L: Length of polarizing plate sample (=300mm)

Then, the amount of curl of the polarizing plate was evaluated based on the following evaluation criteria.
◎: Curl amount C is 0% or more and less than 3% ○: Curl amount C is 3% or more and less than 6% △○: Curl amount C is 6% or more and less than 8% △: Curl amount C is 8 % or more and less than 10% ×: Curl amount C is 10% or more. If it is △ or more, it was judged as good.

(Ring-shaped unevenness in liquid crystal display device)
(1) Production of a liquid crystal display device having a touch panel member Two polarizing plates that had been bonded together in advance were peeled off from a 21.5-inch VAIOTap21 (SVT21219DJB) manufactured by SONY, which is a liquid crystal display device having a touch panel member, and the above production was carried out. The polarizing plates obtained were bonded together to obtain a liquid crystal display device having a touch panel member. The polarizing plates were attached so that the protective film B was on the liquid crystal cell side.

(2) Observation of ring-shaped unevenness The resulting liquid crystal display device was displayed in white, and a plurality of evaluators visually observed the unevenness when viewed from the front and diagonally.
◎: None of the evaluators saw any unevenness. ○: Some evaluators saw slight unevenness, but it was at a level that could be used as a product. △: Many evaluators saw some unevenness, although it was faint. The evaluator also saw unevenness.If it was △ or higher, it was judged as good.

The structures of the obtained polarizing plates 201 to 218 are shown in Table 2, and the evaluation results are shown in Table 3.

As shown in Table 3, the polarizing plates 201 to 204, 208 to 212, 215, and 217 that satisfy the equilibrium water content a of protective film A<the equilibrium water content b of protective film B are all ring-shaped in the liquid crystal display device. It can be seen that the unevenness can be suppressed.

In particular, it can be seen that when the difference in equilibrium water content (ba) is 0.5% by mass or more, ring-shaped unevenness can be more significantly suppressed (comparison between polarizing plates 201 and 203). It is also seen that when the difference in equilibrium water content (ba) is 0.4% by mass or less, curling of the polarizing plate due to the difference in dimensional change can be further suppressed (comparison of polarizing plates 201 to 204).

Furthermore, it can be seen that surface defects can be further suppressed by subjecting not only protective film B but also protective film A to hot water treatment and heat treatment (comparison of polarizing plates 217 and 201).

On the other hand, the polarizing plate 206 where the equilibrium water content a of the protective film A = the equilibrium water content b of the protective film B, and the polarizing plate 207 where the equilibrium water content a of the protective film A > the equilibrium water content b of the protective film B. It can be seen that neither of these methods can suppress ring-shaped unevenness in a liquid crystal display device. Furthermore, it was found that the surface defects of the polarizing plates 218 that were not subjected to the hot water treatment of the protective films A and B were not completely repaired.

According to the present invention, it is possible to provide a polarizing plate that can suppress ring-shaped unevenness in a liquid crystal display device while repairing surface defects of a protective film, a method for manufacturing the polarizing plate, and a liquid crystal display device using the same.

100 Polarizing plate 110 Polarizer 120A, 222, 232 Protective film (Protective film A)
120B, 223, 233 Protective film (Protective film B)
130A, 130B, 225, 235 adhesive layer 140, 224, 234 adhesive layer 200 liquid crystal display device 210 liquid crystal cell 220 first polarizing plate 221 first polarizer 230 second polarizing plate 231 second polarizer 240 backlight 250 liquid crystal display panel

Claims (8)

A polarizer, a protective film A disposed on one surface of the polarizer, a protective film B disposed on the other surface of the polarizer, and a surface of the protective film B opposite to the polarizer. A polarizing plate comprising an adhesive layer disposed on the
The protective films A and B each contain a (meth)acrylic resin and rubber particles,
The (meth)acrylic resin contained in the protective film B contains 50 to 95% by mass of structural units derived from methyl methacrylate, and 1 A copolymer containing ~25% by mass of structural units derived from phenylmaleimide and 1~25% by mass of structural units derived from acrylic acid alkyl ester,
The content of the rubber particles in the protective film B is less than the content of the rubber particles in the protective film A,
The equilibrium moisture content of the protective film A measured at 23°C and 55% RH is a (mass%), and the equilibrium moisture content of the protective film B measured at 23°C and 55%RH is b (mass%). ), the following formula (1) is satisfied,
Polarizer.
Formula (1) a<b The equilibrium moisture content b of the protective film B is 1.5 to 2.0% by mass,
The polarizing plate according to claim 1. The difference (ba) in equilibrium moisture content between the protective film B and the protective film A is 0.5 to 1.5% by mass,
The polarizing plate according to claim 1 or 2. The equilibrium moisture content a of the protective film A is less than 1.5% by mass,
The polarizing plate according to any one of claims 1 to 3. a step of treating the protective film B with hot water of 30°C or higher;
When the glass transition temperature of the protective film B is Tg, heat-treating the treated protective film B at (Tg-70) to (Tg+10)°C;
laminating the heat-treated protective film B on one side of the polarizer, and laminating the protective film A on the other side of the polarizer;
forming an adhesive layer on the surface of the protective film B opposite to the polarizer;
has
The protective film B includes a (meth)acrylic resin and rubber particles,
The (meth)acrylic resin contains 50 to 95% by mass of structural units derived from methyl methacrylate and 1 to 25% by mass of phenylmaleimide based on the total structural units constituting the (meth)acrylic resin. A copolymer containing a structural unit derived from and a structural unit derived from 1 to 25% by mass of an acrylic acid alkyl ester,
The equilibrium moisture content of the protective film A measured at 23°C and 55% RH is a (mass%), and the equilibrium moisture content of the protective film B measured at 23°C and 55%RH is b (mass%). ), the following formula (1) is satisfied,
A method of manufacturing a polarizing plate.
Formula (1) a<b a step of treating the protective film A with hot water of 30° C. or higher;
a step of heat treating the treated protective film A at (Tg-70) to (Tg+10)°C;
It further has
bonding the heat-treated protective film A to the other surface of the polarizer;
The method for manufacturing a polarizing plate according to claim 5 . liquid crystal cell,
a first polarizing plate disposed on one side of the liquid crystal cell;
a second polarizing plate disposed on the other surface of the liquid crystal cell;
has
At least one of the first polarizing plate and the second polarizing plate is the polarizing plate according to any one of claims 1 to 4 ,
The adhesive layer of the polarizing plate is bonded to the liquid crystal cell,
LCD display device. The liquid crystal cell is an IPS type liquid crystal cell,
The liquid crystal display device according to claim 7 .

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